Hotwire-directed energy deposition (HDED) is a promising method to other additive techniques in large-format applications. In HDED, wire is heated up close to melting temperature by resistance and laser energy is used to melt the substrate surface to form a metallurgical bond. This method can improve the stability and productivity of the process while reducing overall heat input and maintaining proper mechanical properties. A limitation in traditional hotwire-directed energy deposition is the directional dependence. The wire is fed from the side into the puddle formed by the laser. The dimensional relationship between the wire and laser is critical and changes when the direction of travel is altered. A solution to this challenge is feeding the wire coaxially to the process. The laser spot is split into three separate dots and converge to a common tool center point (TCP). The wire is fed through the center of the laser process head and joins the laser spots at the common TCP. Inconel 625 and Titanium 6/4 will be evaluated as material characterizations. Inconel 625 is a nickel-based superalloy combining corrosion resistance and high strength. Titanium 6/4 is also corrosive resistance but is highly valued for its high strength to weight ratio. The dynamics of the puddle and preheating process of wire have been visualized by a high-speed camera. The microstructure of deposition has been investigated by optical microscope, the chemical composition has been measured by energy dispersive spectroscopy (EDS) and the hardness has been tested by micro-hardness tester.
- Understand the benefits of laser hotwire with regards to material properties, build times and material utilization
- Describe the challenges of side feeding wire and the flexibility in path planning provided by coaxially delivered wire
- Define key elements of building large-format parts and the pros and cons of various processes